data( iris )set.seed( 20090415 )mod <- gbm(Species ~ .,            data              = iris,            distribution      = "multinomial",           n.tree            = 5000,            shrinkage         = 0.001,            cv.folds          = 2,           bag.fraction      = 0.8,           interaction.depth = 3,           verbose = FALSE)gbm.perf( mod, method="cv" )mod